As delegates confer at the U.N. climate summit in Copenhagen, an action taken in Washington on Monday will likely mark the week's most important progress in addressing the effects of global warming.
 
On the same day the Copenhagen summit began, the U.S. Environmental Protection Agency (EPA) announced that carbon dioxide and other greenhouse gases endanger human health and welfare, triggering a regulatory process to deal with emissions from power plants and other industry, cars and agriculture.
 
The EPA's "endangerment" finding is a game changer, moving the issue into the realm of direct health effects on you and your neighbor rather than the amorphous matter of how warming may be affecting earth somewhere else.

"Public health issues are often more compelling to people than things they don't experience directly or they think are years off," said Bill Grant, Midwest director of the Izaak Walton League. "If Congress wasn't convinced before that EPA would act, they should no longer be under that delusion." 
 
Political dangers in moving fast
Already, members of Congress are expressing fears of hasty bureaucratic meddling and unwanted burdens as the nation struggles through economic recovery. Major actions like EPA's invariably lead to congressional pushback, and administration officials know the political danger of moving ahead too fast with any regulatory effort.
 
Industry advocates are threatening to sue to prevent regulatory impositions; some even question the scientific basis for EPA's finding. Others see the timing of EPA's action as evidence that President Barack Obama intends to go to Copenhagen next week and show the world that one of the world's top polluters is ready to step up and lead after 12 years of dallying in denial and delay since the last the last major climate summit in Kyoto, Japan.
 
While EPA's action will surely lead to high-level push-pull, there's reason to believe that an "endangerment" finding puts the Obama administration in a strong position to take significant steps to reduce carbon and other emissions.
 
Here's why:
 
• The EPA action is on solid legal footing. In 2007 the U.S. Supreme Court, in a case brought in Massachusetts by more than a dozen advocacy groups, ruled that carbon and other greenhouse gasses are pollutants under the 1990 federal Clean Air Act and must be regulated. The case has been exhaustively litigated for a decade, making the success of further appeals unlikely.   
 
• The Congress itself passed the Clean Air Act and the Energy Policy and Conservation Act, which provide a strong basis for rule-making to deal with health-based air-quality threats including carbon from automobiles.
 
• The public understands health effects of degraded air; people can see sullied skies and they know that respiratory ailments are caused and aggravated by air pollution. If Congress seeks to rein in the EPA, it would have to undo laws that it has already painstakingly considered and passed with broad public support.

EPA to focus on big polluters
For its part, the EPA has indicated it will proceed carefully.

"We can begin reducing emissions from the largest greenhouse gas emitting facilities without placing an undue burden on the businesses that make up the vast majority of our economy," said EPA Administrator Lisa Jackson. She said rules would target only the largest sources — industry and transportation — responsible for nearly 70 percent of U.S. greenhouse gas emissions. 
 
This means that coal-fired power plants will likely continue to switch to natural gas from coal, that future plants like the recently canceled Big Stone II power plant won't be built, that large plants will be required to reduce carbon emissions, and that cars and light trucks will have much more stringent tailpipe-emission controls by 2016.
 
Politically tougher emissions — like methane from agriculture and landfills — likely won't be included in the first regulatory round.
 
In the nearer term, watch what President Obama tells the U.N. summit next week in Copenhagen, and how the U.S. Senate responds. Two major measures to deal with carbon emissions — a cap-and-trade bill and a milder climate-change bill — continue to languish. 
 
Regarding the EPA's action, Sen. John Kerry, D-Mass., said "the message to Congress is clear — get moving."